The tires supporting a car body are installed at a predetermined angle, that is, at a predetermined camber angle and toe-in angle, to the right and left ends of an axle by means of their associated wheels. These angles are required to be within respective predetermined ranges. The camber angle is necessary to prevent the tire from being disengaged from the wheel installed on the axis when the weight of the car body is applied. With the camber angle, the tires are positioned on the ground surface to be inclined divergently from the ground surface, namely, their tops are projected slightly outward from the bottoms in contact with the ground surface. The toe-in angle is required for securing the linear running of the car and is such that the distance between the front portions of the right and left tires is smaller than that between the rear portions. In other words, when viewed from above, the right and left tires are converged frontally of the car. The camber and toe-in angles are very important factors in safe driving of the car. Thus, it is legally required that these angles should be accurately measured and readjusted after the tires are installed or during car inspection, etc.
In these circumstances, a variety of apparatuses and methods have been proposed for such a measurement.
For example, an apparatus for measuring the toe-in length or angle and camber angle is known which has a plate or the like to be put in contact with a tire immovably positioned in place to measure the camber and toe-in angles with a measuring means such as manometer or the like.
With such measuring apparatus, however, the relieved markings of a manufacturer's name, standard, etc. provided on the tire surface with which the plate is placed in contact cause an error in the measurement and thus make it impossible to accurately measure the tire angles. Also in this measuring apparatus, since the plate is put in direct contact with the tire, any slight movement of the tire during measurement will possibly cause an error in measurement and the elaborated measuring apparatus to be damaged.